This application relates to dielectric overshoes for use by electrical workers, and more particularly relates to an improved dielectric overshoe that has a combination of rubber compositions and overshoe configurations such that it gives adequate protection and long-wearing use to a wearer.
Dielectric boots are known that are formed of various rubber compositions. These boots are either of the overshoe type which are worn over the footwear of a wearer or a type which cover the foot of the worker in place of a shoe. These prior art boots typically have an open tongue and hang loosely about the wearer's ankle.
In addition, there were prior art boots that covered only the foot and that were buckled closed. However, these may not have been dielectric boots formed of rubber to provide insulation to an electrical worker. In addition, dielectric boots may have been known that cover the wearer's leg up to a point below the knee and which had fasteners to close the front of the boot.
In general, the prior art boots are undesirable in that they either did not provide sufficient dielectric qualities, or might allow seepage of liquids, such as water, into the boot since it was not tightly sealed about a wearer's ankle. In addition, these prior art boots were not always compatible with various climbing equipment that is commonly used by electrical workers.
Standards have recently been enacted by the American Society of Testing Materials to provide requirements for overshoe footwear that is to be labeled as "dielectric overshoe footwear". These standards, ASTM F 1117-87, relating to "Rubbers", designed to be worn over existing footwear and to cover only the foot of the worker, require that an overshoe "Rubber" be given an electric proof test, and withstand a 60-Hz alternating current proof test voltage, or a direct current proof-test voltage. The proof test are applied continuously to the overshoe for a minimum of one minute to a maximum of three minutes. The alternating current proof test for "Rubbers" provides a 15,000 voltage proof-test voltage, and the direct current proof-test is 45,000 volts.
There are various procedures for testing an overshoe. In a first procedure, an overshoe is filled with water, or a conductive metal shot, so that the inner sole is completely covered. The overshoe is then placed in water to a depth such that the underside of the sole is in contact with the water without the water going above the top part of the sole. The water, or metal shot, inside the footwear forms one test electrode and is connected to one terminal of a voltage source by means of a chain or a sliding rod that dips into the water, or metal shot, in the overshoe. The water in the container outside the overshoe forms the other electrode and is connected directly to the other terminal of the voltage source.
When this procedure is utilized, a test reading of one mA between the electrodes indicates that the shoe has failed the test.
Another test procedure is utilized in which the footwear is immersed to a level even to the top of the foot. With this test procedure, a current reading of 10 mA is allowed before the shoe fails the test.
It has proven difficult for many of prior art overshoes, or "Rubbers", to meet these test standards.
Thus, it is an object of the present invention to disclose a dielectric overshoe that can meet the testing standards noted above and in addition, will provide long-wearing use to a wearer.
Also, it is an object of the present invention to disclose an improved dielectric overshoe that is compatible with various types of climbing equipment that are commonly used by electric workers.